1. Field of Invention
The present invention relates to a projection lens unit including a plurality of lenses disposed along a given axis, which enlarges and projects an input optical image, and relates to a projector using the projection lens unit.
2. Description of Related Art
Hitherto, a projector has been known which includes a light source, an electrooptical unit for forming an optical image by using a light beam from the light source, and a projection lens unit for enlarging and projecting the image formed by the electrooptical unit.
The projector is widely used for presentation by multimedia in public meetings, such as conferences, academic meetings, and exhibitions.
The projector is maintained in an installed manner in a conference room, or the like, for presentation, or is brought to the conference room as needed. The projector may occasionally be removed to another place to be stored after use. Therefore, the portability must be improved so as to be easily transported. The device is required to be reduced in size and to have a low-profile.
Accordingly, the present invention provides a projection lens unit enabling a projector, which is reduced in size and which has a low-profile, and to provide a projector using the projection lens unit. A projection lens unit according to the present invention may include a plurality of lenses which are disposed along a given axis, and enlarges and projects an input image. At least one of the plurality of lenses disposed at the base end opposite to the projection direction is formed to be cut away at the upper portion.
In the projection lens unit according to the invention, the height of a member which supports the projection lens unit can be reduced because of the lens being cut away at the upper portion and the cut-away surface being made substantially flat. A component, such as a cooling fan, can be mounted without interfering with the lens, over an electrooptical unit disposed in the vicinity of the base end of the projection lens unit. With this arrangement, the height of a projector including the projection lens unit can be reduced, and it is not necessary to provide an additional space in the projector for receiving a cooling fan, or the like, whereby the projector can be designed to have a reduced size and a low-profile.
When the projector is configured so that the center of an image-forming region of the electrooptical unit for forming an optical image in accordance with image information is disposed below the intersection of a line extending from the axis of the projection lens unit and an optical modulation unit, the optical image from the electrooptical unit is applied to a point below the axis, transmitted through the projection lens unit, and projected to be expanded toward an area higher than the axis. Therefore, the optical image is enlarged and projected on a projection area without any problem when a lens disposed at the base end opposite to the projection direction is cut away at the upper portion.
According to the invention, a flange, which protrudes toward the outside in the radial directions, is preferably provided at the periphery of the projection lens unit, the flange being provided at the base end toward the other end of the projection lens unit.
In a projection lens unit having such a flange, an opening, in which a base end of the projection lens unit is inserted, must be formed in a supporting member of the projection lens unit for the flange to be fixed to the supporting member by screws. In the projection lens unit according to the present invention, the lens is cut away at the upper portion thereof so that the size of the opening in the supporting member can be reduced, thereby miniaturizing the supporting member.
By fixing the projection lens unit in a manner described above, the projection lens unit can be fixed at a position in the vicinity of the center of gravity of the projection lens unit, whereby the projection lens unit can be fixed to the supporting member in a stable manner.
According to the present invention, the projector may include an electrooptical unit for forming an optical image in accordance with image information. The projector may include the projection lens unit described above, whereby the same effect is obtainable as in the projection lens unit.
The projector preferably includes a supporting member for supporting the projection lens unit at a base end thereof, and an opening through which the lens is inserted, the opening being formed in accordance with the shape of the base end of the projection lens unit.
With this arrangement, the ratio of the sizes of the opening to the supporting member can be reduced, whereby sufficient strength can be ensured when the supporting member is made thin.
In the projector according to the present invention, the center of an image-forming region of a light modulation unit forming the electrooptical unit may be disposed below the intersection of a line extending from the axis of the projection lens unit with the light modulation unit.
With this arrangement, as described above, the optical image is applied to a lower part and is emitted toward an upper part through the projection lens unit. The optical image can be enlarged and projected on a projection area without any problem when the lens disposed at the base end opposite to the projection direction is cut away at the upper portion thereof.